This invention relates to methods of modifying the mounting tension of an artist""s canvas.
An artist""s canvas is produced by mounting a canvas under tension on a rigid frame. Such canvas is known to develop sags or puckers. This is due to the applied tension being insufficient or nonuniformly distributed throughout the canvas. A common method of removing the sags and puckers is to use a frame constructed from stretcher bars that have mortised corners. Wedge-shaped tenons in the mortises are used to expand the frame to adjust the tension of the canvas.
The present invention comprises a method of modifying tensile stresses in an unpainted canvas that is mounted on a frame under applied tensile stresses. The canvas is formed of material that can undergo heat-shrinking when at or a above a thermoplastic shrinking temperature, and can undergo heat-softening when at or above a thermoplastic softening temperature. The method comprises heating the canvas to a temperature at or above the thermoplastic shrinking temperature and the thermoplastic softening temperature. The method further comprises maintaining the canvas of a temperature at or above the thermoplastic shrinking and softening temperatures. This induces heat-shrinking, and thereby increases the tensile stresses in any portions of the canvas in which the applied tensile stresses are less than the opposing stresses of the heat-shrinking. This also induces heat-softening, and thereby decreases the tensile stresses in any portions of the canvas in which the applied tensile stresses are grater than the opposing stresses of the heat-shrinking. The method further comprises subsequently cooling the canvas to a temperature below the thermoplastic shrinking and softening temperatures, whereby the canvas becomes set in a condition of modified tensile stresses.
In a preferred embodiment, the canvas is maintained free of any softening agent throughout the heating and maintaining steps. The frame is maintained without dimensional adjustment throughout the heating and maintaining steps. The material has warp yarns formed of a first component that can undergo heat-shrinking when at or above the thermoplastic shrinking temperature, and can also undergo heat-softening when at or above the thermoplastic softening temperature. An equal number of weft yarns are formed of the first component. The first component is preferably polyester. The material further includes a second component that does not heat-shrink at the thermoplastic shrinking temperature. The second component is preferably cotton. The frame comprises four strainer bars connected together by fasteners to form fixed joints. Alternatively, the frame comprises four stretcher bars connected together by mortised joints that enable expansion of the frame. The canvas is fixed to the frame by fasteners in a permanent condition suitable for the canvas to be subsequently painted while fixed to the frame.